This invention relates to an exposure method and apparatus suitably usable, for example, for the manufacture of semiconductor devices such as ICs or LSIs. In another aspect, the invention is concerned with a device manufacturing method for manufacturing microdevices by using such an exposure method or apparatus.
An exposure apparatus is used to expose a wafer having a resist applied thereto to a pattern of a semiconductor chip (e.g., an IC or on LSI) with exposure light. In this exposure process, a portion of the exposure light is detected by using a light dividing element which is disposed along the path of the exposure light from a light source and which is placed between the light source and the semiconductor chip pattern. On the basis of the light detection, the integrated quantity of the partial light is measured and a amount of exposure is control. Such exposure controlled is done on an assumption that the ratio of the intensity of the partial light to the intensity of the exposure light impinging on the wafer is constant.
However, the applicant has found that, during repetition of the exposure process using the exposure apparatus, the light absorptivity of a condenser lens which may be disposed between the light dividing element and the semiconductor chip pattern and/or the light absorptivity of a projection optical system for projecting the chip pattern onto the wafer may change, and that, as a result, the ratio of the intensity of the partial light mentioned above to the intensity of the exposure light impinging on the wafer may change. If it changes, then correct exposure control is not attainable.
It is accordingly an object of the present invention to provide an improved exposure method and/or apparatus by which the amount of exposure can be controlled precisely.
It is another object of the present invention to provide an improved device manufacturing method based on such an exposure method or apparatus.
In accordance with an aspect of the present invention, there is provided an exposure method wherein exposures are made repeatedly, said method comprising the steps of: controlling an amount of exposure on the basis of detection of an integrated light quantity of a portion of exposure light used for an exposure; and detecting, in response to completion of each exposure or exposures of a determined number, a ratio in intensity between the exposure light upon a substrate being exposed and the portion of the exposure light, which ratio is used for the exposure amount control.
In accordance with another aspect of the present invention, there is provided an exposure apparatus, comprising: a light dividing means disposed along a path of exposure light to extract a portion of the exposure light; exposure control means for detecting an integrated light quantity of the portion of the exposure light extracted by said light dividing means, to control the amount of exposure; and ratio detecting means for detecting, in response to completion of each exposure or a predetermined number of exposures, a ratio in intensity between the extracted portion and the exposure light upon a substrate, which ratio is used for the exposure amount control.
In accordance with a further aspect of the present invention, there is provided an exposure method wherein exposures are made repeatedly, said method comprising the steps of: controlling an amount of exposure on the basis of detection of an integrated light quantity of a portion of exposure light used for an exposure; and detecting a change in ratio between the intensity of the exposure light upon a substrate being exposed and the intensity of the portion of the exposure light.
In accordance with a still further aspect of the present invention, there is provided an exposure apparatus, comprising: a light dividing means disposed along a path of exposure light to extract a portion of the exposure light; exposure control means for detecting an integrated light quantity of the portion of the exposure light extracted by said light dividing means, to control the amount of exposure; and detecting means for detecting a change in ratio between the intensity of the extracted portion and the intensity of the exposure light upon a substrate.
In one preferred form of an exposure method or apparatus of the present invention, a first photodetector is used to receive the portion of the light to produce a signal corresponding to the intensity of the received light. A second photodetector having a light receiving surface disposed substantially at the same level as the substrate is used to receive the exposure light to produce a signal corresponding to the intensity thereof. The intensity ratio is determined on the basis of these signals.
In another preferred form of an exposure method or apparatus of the present invention, the intensity ratio is determined on the basis of information which concerns changes in transmissivity, with respect to the exposure light, of an optical system for projecting the exposure light to the substrate after the portion being extracted.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.